Yahoo's traffic does not include data from Tumblr, acquired by Yahoo earlier this year for $1 billion, says comScore. Microsoft properties, Facebook and AOL rounded out the top five.

Granted, the rare monthly win for Yahoo does not include search and mobile results. But it is, by any measure, a landmark achievement for a company left for dead by many.

Yahoo and Google declined comment on the comScore report.

"Hire and retain a great team; build inspiring products that will attract users and increased traffic; that traffic will increase advertiser interest and ultimately translate to revenue," Mayer said in a recent call with analysts.

It won't be easy with formidable foes such as Google and Facebook. Yahoo's second-quarter revenue slipped 1% to $1.07 billion, missing analysts' estimates of $1.08 billion.

Clearly, Mayer has put the exclamation point back into the Internet icon. (Though that might change, or at least be altered, when Yahoo debuts its new logo after Labor Day.)

Something more is going on at Yahoo: Shares have nearly doubled in value since Mayer took over; it has acquired Tumblr and other valuable properties; and Yahoo has refreshed its product line. Mayer even found time to polish her fashion bona fide as a fashion in an eye-popping Vogue photo spread and profile this month.

The earnest Wisconsin native won't crow about Yahoo's July surprise -- Yahoo is grappling with the mobile puzzle, as are its rivals -- but don't begrudge her if she and her team celebrate privately.